ValueError : String 1 ... cannot be simplified to a number!

Asked by A E K on 2018-03-08

I am testing a new model of 6 dimensional DM model, with a fermionic, SM singlet DM field.
And, I define DM field as a Dirac fermion, with 70 GeV mass and zero width.
The operators seperated in two parts, while in one part the SM particles (e,u,d) are included as a singlet, in another part SM fermions included as a doublet (l and q). While generating UFO output,in Feynrules, I took SM singlet particles as u,d,e and SM doublets as uL,dL and eL. It didnt give me any certain error in FR.

After importing model and defining darkmatter candidate, I try to generate relic density.
While getting output I get an error with this:

Command "output" interrupted with error:
ValueError : String 1 T(4,3) cannot be simplified to a number!
Please report this bug on
More information is found in 'MG5_debug'.
Please attach this file to your report.

I've attached the debug file as MG_debug_2 in the MG_debug.tgz file.

Could you please help me if this is originated from my model or a bug.


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Do you have any gluon in your model?
Does it couple to all QCD charged particle?

I'm asking that since we have since years an issue with FR with the color representation.
Fr does not distinguish what is 3 and 3bar and just assume that all particle are 3 and all anti-particle are 3bar.

The problem is that many people does not follow such convention and the FR produces some bad UFO model without any warning/error.

To minimise the problem, we decide in MG5aMC to still allow those model when possible (and therefore to correct them on the flight).
For doing that we analyse the interactions with a color octet and see if we need to flip the 3/3bar representation for some particle.
If such interactions does not exists, then we do not apply such check and if the information is not correct then it can lead to the crash similar that you see above.



PS: attachment are not working for question. If you want to attach a file, you need to create a bug report.

A E K (elcikud) said : #2


I don't have any gluon in my model.
My fermionic dark matter field just couples to all SM quarks and leptons via two types of operator form.

I think I should try to implement the color representation properly, and, may get some support from FR team.

Thanks for your help,

PS: my MG5_debug link is:

Can you help with this problem?

Provide an answer of your own, or ask A E K for more information if necessary.

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